Paste-type nickel electrodes useful as a positive electrode in an alkaline storage battery have been developed in the industry to replace sintered-type nickel electrodes. These conventionally known nickel electrodes are manufactured by first mixing a nickel hydroxide powder with a cobalt or nickel powder which serves as an electroconductive agent. Thereafter, an aqueous solution of a thickener, such as carboxymethylcellulose (CMC), is added to the mixture and kneaded to provide a pasty material. The pasty material is then applied to a foam nickel base plate or substrate, or to a fibrous nickel felt, net-like or latticed porous metal base plate or substrate, so that the substrate is impregnated and/or coated with the pasty material. The substrate is then dried and pressed to obtain a paste-type nickel electrode plate. This electrode plate is used as a positive electrode in an alkaline storage battery, such as a nickel-cadmium storage battery, a nickel hydrogen battery or the like.
With the increased use and demand of portable electrical instruments and appliances in recent years, a strong demand has arisen for an alkaline storage battery that has a high-capacity performance and particularly for a battery having a high-performance nickel electrode. It is generally known, however, that paste-type nickel electrodes are inferior with respect to their coefficient of utilization, rapid or quick discharge characteristics, and length of service life as compared to sintered-type nickel electrodes. To avoid these drawbacks, it has been proposed that, for the purpose of enhancing the conductivity and minimizing polarization within the battery, an active material of primarily nickel hydroxide powder be prepared containing a small amount of cobalt hydroxide and, additionally, a nickel (Ni) powder, a cobalt (Co) powder, a cobalt oxide (CoO) powder or the like as an electroconductive material. This mixture is prepared with an aqueous solution of thickener as described above with respect to conventional paste-type nickel electrodes. However, an alkaline storage battery having overall good performance has not been obtained utilizing such an electrode.
More particularly, sealed-type nickel-hydrogen alkaline storage batteries which have been manufactured comprise a battery element having a paste-type nickel positive electrode containing a small amount of Co or CoO as an active electroconductive material and a hydrogen-occlusion electrode as a negative electrode. The positive and negative electrodes are stacked one upon another with a separator interposed between the electrodes. An alkaline electrolyte solution having a concentration as high as approximately 30 wt. % is utilized therewith. The battery still had a calculated coefficient of utilization lower than a satisfactory level for both the battery capacity and the rapid discharge capacity. The coefficient of utilization as utilized herein defines the relationship between the actual battery capacity obtained and the theoretical capacity of the battery's positive electrode. Additionally, the battery's cycle life is short. A battery having improved performance characteristics in these areas, therefore, would be advantageous.